Stormwater Manual Revisions

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Olympia adopted its 2005 Stormwater Manual in anticipation of the NPDES Phase II Permit being issued by the Washington State Department of Ecology (WDOE). The permit requires implementation of specific stormwater management programs including regulations for new developments. The current manual is based upon the Washington State Department of Ecology's 2001 Western Washington Stormwater Manual.

Why are We Making Changes to the Stormwater Manual?

To be in compliance with the now-released NPDES Permit, the City must adopt a manual which is equivalent to the 2005 WDOE Manual. Most of the proposed 2009 changes provide this equivalency. Other proposed revisions respond to community concerns. A Public Hearing was held in July 2009; the Stormwater Drainage Manual is scheduled on the Council consent calendar for adoption in late October 2009.

What are the Major and Minor Issues and Clarifications?

Major issues have the potential to significantly impact short- or long-term costs for private and public construction projects. These issues could impact existing City policies. Proposed minor revisions will result in some small change to design and/or operation of facilities that are are already required. Proposed clarifications tie together existing manual requirements or add explanations to existing requirements. Nothing new is being required in a clarification.

What are the Major Issues?

City staff has identified five potential revisions that involve major policy and regulatory issues. Download our printer-friendly documents (PDF format) to review the issues documents and technical memos.

  1. Redevelopment Thresholds for: Private Projects - Olympia requires private and public properties undergoing significant upgrades to buildings and sites to bring stormwater conveyance, detention, and treatment up to current standards.
  2.  Roadway Projects - Various public roadway projects are required to bring stormwater conveyance, detention, and treatment up to current standards.
  3. Clearing and Grading Restrictions - Clearing and grading regulations address mass erosion and associated sediment
    depositions in streams and wetlands, a well-documented urban impact.
  4. Pond Design - Olympia stormwater ponds tend to maximize hydraulic function while minimizing other functions, including
    aesthetics.
  5. Infiltration Rate Determination - accurate infiltration rates are needed to correctly size ponds, thereby mitigating flooding and downstream environmental impacts.
  6. Wellhead Protection Areas - Drinking water supplies are vulnerable to pollution from infiltrated stormwater.

Contacting Public Works: